1. Field of the Invention
The present invention relates to a fuel injection device, and more particularly to an electronically controlled fuel injection device employed by an internal combustion engine mounted on a two-wheeled vehicle or other vehicle.
2. Description of the Related Art
Conventionally, in an internal combustion engine mounted on a two-wheeled vehicle or other vehicle, for example, a so-called fuel injection device is employed, which, while pressurizing fuel by means of a fuel injection pump, feeds the fuel to a fuel injection nozzle and supplies the fuel to an intake path following atomization in the fuel injection nozzle.
Also, in order to feed fuel to the fuel injection device, the fuel injection device and the fuel tank where the fuel is retained are coupled by means of a fuel supply pipe.
In this connection, in a conventional fuel injection device of this kind, when the temperature of the fuel rises as a result of a rise in the ambient temperature, for example, vapor is produced within the fuel.
Further, when the vapor amount exceeds the discharge capacity of the fuel injection pump, there are problems such as control of the fuel supply amount being adversely affected.
In order to improve such problems, in the prior art, a fuel pump that supplies fuel is disposed upstream of the fuel injection pump, and fuel is continuously pressurized at or above a prescribed pressure by means of this fuel pump.
This handling method involves liquefaction of the vapor by pressurizing the fuel at or above a prescribed pressure, such that the liquefied vapor is contained within the fuel.
However, with a vapor elimination method using fuel pressurization of this kind, the following problems remain unsolved.
That is, in the handling method described above, in order that fuel within the fuel supply path arriving at the fuel injection pump should be continuously held at or above a prescribed pressure, as described hereinbelow, a fuel pump other than a fuel injection pump is necessary. The high pressure created by this fuel pump makes it necessary for the fuel supply path to be formed using a high-pressure pipe or a high-pressure hose, or the like. The use of such high-pressure pipe or high-pressure hose disadvantageously causes the manufacturing costs to rise sharply.
Further, since the fuel must be kept in a pressurized condition even when the internal combustion engine has been stopped, the burden on the device is considerable, and this is undesirable also in terms of durability.